Gemma Frisius

Gemma Frisius (born Jemme Reinerszoon)[1] (December 9, 1508 – May 25, 1555), was a physician, mathematician, cartographer, philosopher, and instrument maker. He created important globes, improved the mathematical instruments of his day and applied mathematics in new ways to surveying and navigation.

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Frisius was born in Dokkum, Friesland (present-day Netherlands), of poor parents who died when he was young. He moved to Groningen and studied at the University in Leuven beginning in 1525. He received the degree of MD in 1536 and remained on the faculty of medicine in Leuven for the rest of his life. His oldest son, Cornelius Gemma, edited a posthumous volume of his work and continued to work with Ptolemaic astrological models.

While still a student, Frisius set up a workshop to produce globes and mathematical instruments. He became noted for the quality and accuracy of his instruments, which were praised by Tycho Brahe, among others. In 1533, he described for the first time the method of triangulation still used today in surveying. Twenty years later, he was the first to describe how an accurate clock could be used to determine longitude. Jean-Baptiste Morin (1583–1656) did not believe that Frisius' method for calculating longitude would work, remarking, "I do not know if the Devil will succeed in making a longitude timekeeper but it is folly for man to try."[2]

Gemma Frisius's 1533 diagram introducing the idea of triangulation into the science of surveying. Having established a baseline, e.g. the cities of Brussels and Antwerp, the location of other cities, e.g. Middelburg, Ghent etc., can be found by taking a compass direction from each end of the baseline, and plotting where the two directions cross. This was only a theoretical presentation of the concept — due to topographical restrictions, it is impossible to see Middelburg from either Brussels or Antwerp. Nevertheless, the figure soon became well known all across Europe.